Combined transplantation of neural stem cells and olfactory ensheathing cells for the repair of spinal cord injuries.

Spinal cord repair is a problem that has long puzzled neuroscientists. The failure of the spinal cord to regenerate and undergo reconstruction after spinal cord injury (SCI) can be attributed to secondary axonal demyelination and neuronal death followed by cyst formation and infarction as well as to the nature of the injury environment, which promotes glial scar formation. Cellular replacement and axon guidance are both necessary for SCI repair. Multipotent neural stem cells (NSCs) have the potential to differentiate into both neuronal and glial cells and are, therefore, likely candidates for cell replacement therapy following SCI. However, NSC transplantation alone is not sufficient for spinal cord repair because the majority of the NSCs engrafted into the spinal cord have been shown to differentiate with a phenotype which is restricted to glial lineages, further promoting glial scaring. Olfactory ensheathing cells (OECs) are a unique type of glial cell that occur both peripherally and centrally along the olfactory nerve. The ability of olfactory neurons to grow axons in the mature central nervous system (CNS) milieu has been attributed to the presence of OECs. It has been shown that transplanted OECs are capable of migrating into and through astrocytic scars and thereby facilitating axonal regrowth through an injury barrier. Given the complementary properties of NSCs and OECs, we predict that the co-transplantation of NSCs and OECs into an injured spinal cord would have a synergistic effect, promoting neural regeneration and functional reconstruction. The lost neurocytes would be replaced by NSCs, while the OECs would build "bridges" crossing the glial scaring that conduct axon elongation and promote myelinization simultaneously. Furthermore, the two types of cells could first be seeded into a bioactive scaffold and then the cell seeded construct could be implanted into the defect site. We believe that this type of treatment would lead to improved neural regeneration and functional reconstruction after SCI.

Protective effects of extract of Ginkgo biloba (EGb 761) on nerve cells after spinal cord injury in rats.

STUDY DESIGN: An experimental animal model was used to assess spinal cord injury following lateral hemitransection at thoracic spinal cord level. OBJECTIVE: To determine whether extract of Ginkgo biloba (EGb) could have a neuroprotective effect in spinal cord injury (SCI) in rats. SETTING: Department of Biological Sciences and Biotechnology, Tsinghua University, China. METHODS: A total of 72 adult rats were divided randomly into three groups: the EGb group, normal saline (NS) group, and sham operation group (sham group). After thoracic spinal cord hemitransection was performed at the level of the 9th thoracic vertebra (T9), rats in the EGb group were given 100 mg/kg EGb 761 daily, while rats in the NS group received NS. The rats in the sham group only underwent laminectomy without spinal cord hemitransection. At various time points after surgery, thoracic spinal cords were sampled and sliced for histochemistry, immunohistochemistry of inducible nitric oxide synthase (iNOS), and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) of apoptotic cells. RESULTS: Myelin staining showed that the area of cavities was small and the demyelinated zones were limited at and around the injury site of the spinal cord in the EGb group, while the area of cavities was large and the demyelinated zones were serious in the NS group. Nissl staining showed that the ratio of bilateral ventral horn neurons (transection side/uninjured side) in the EGb group was higher than that in the NS group (P<0.05). The apoptotic index and the percentage of iNOS-positive cells were lower in the EGb group than in the NS group. Furthermore, the percentage of iNOS-positive cells positively correlated with the apoptotic index (r( 2)=0.729, P<0.01) after SCI. CONCLUSION: This study demonstrated that EGb 761 could inhibit iNOS expression and have neuroprotective effect by preventing nerve cells from apoptosis after SCI in rats.

Neural stem/progenitor cells survive and differentiate better in PD rats than in normal rats.

To investigate the effects of grafted neural stem/mesencephalic progenitor cells (NSCs/MP) on rotational behavior of Parkinson's disease (PD) rats and the influence of intracerebral environment on NSCs/MP, we observed the survival and differentiation of NSCs/MP transplanted into 6-hydroxydopamine (6-OHDA)-lesioned and intact striatums. NSCs/MP were prepared from E(11-15) rats and proliferated in serum-free medium with bFGF for several weeks. One day after being primed with serum/dbcAMP to differentiate, cell suspensions were grafted into 6-OHDA-lesioned and intact striatums respectively. It had been found that NSCs/MP were able to survive better and differentiate into more tyrosine hydroxylase (TH)-positive neurons in 6-OHDA-lesioned striatums than in intact ones, and apomorphine-induced rotations were obviously attenuated in MP graft models. The data suggested that NSCs/MP tend to survive and differentiate into TH-positive neurons in 6-OHDA-lesioned striatums. The data demonstrated that striatums in which DAergic terminals are destroyed by 6-OHDA undergo some changes and thus provide more appropriate conditions for NSCs/MP to differentiate into mature DAergic neurons. Furthermore, the finding that MP had greater relieving effects on rotational behavior than NSCs suggests that NSCs could not be used in clinical therapy of PD unless being induced into MP in vitro before transplantation.

Mesencephalic progenitors can improve rotational behavior and reconstruct nigrostriatal pathway in PD rats.

The aim of this study was to investigate the possibility of mesencephalic progenitors (MP) in treating Parkinson's disease (PD). MP were prepared from E(11-13) rats and proliferated in serum-free medium with basic fibroblast growth factor (bFGF) for 10 days. Cells were then collected and implanted into the striatum only--single grafts or simultaneously into the substantia nigra (SN) and the striatum--double grafts. Twelve weeks after transplantation, DiI, a fluorescent dye, was microinjected into the ipsilateral striatum. Using this strategy, it was found that MP of double grafts had more potent effects on rotational behavior than that of single grafts. Injection of the retrograde tracer DiI into the striatum resulted in fluorescent-labeled cells within the intranigral grafts in double grafts. These data greatly support that MP transplants could not only improve rotational behavior, but does help to re-establish nigrostriatal connections so that it may become one efficient way in treating PD.